Phosphofructokinase (PFK; EC.2.7.1.11) exists in tetrameric isozymic forms in man and a number of vertebrate species. Three structural loci encode three distinct subunits, M (muscles, L (liver) and P (platelet) types. In man, inherited deficiency of muscle PFK in the homozygous state is associated with exertional myopathy and hemolysis (glycogen storage disease type VII) where as the heterozygous state results in a clinically silent carrier state. Recently, we have described the occurrence of inherited muscle PFK deficiency among English Springer Spaniel dogs. Curiously unlike their human counterparts, the deficient dogs exhibit the presence of a more severe hemolytic syndrome but an apparent absence of muscle disease. These atypical features are shown to result from a unique nature of isozyme distribution pattern and muscle physiology in the dog as well as a compensating retention or reexpression of liver isozyme by the probands. We now wish to investigate in greater detail this animal model of a human glycolytic enzymopathy to assess its experimental usefulness. Specifically, we wish to undertake the following studies: (1) Establishment of a small breeding colony of PFK-deficient dogs and eventually development of a hyperuricemic dog; (2) Routine hematological and biochemical studies; (3) Assessment of the glycolytic competence of these dogs; (4) Definition of the PFK isozymic profile of blood cells, cultured cell lines, and solid organs; (5) Metabolic studies of muscle; (6) Developmental studies of canine muscle and erythrocytes; (7) Immunocytologic, histochemical and electron microscopic studies of muscle. The techniques and/or reagents necessary for these studies are well-established/available in our laboratories. These studies are expected to characterize in greater detail this animal model of a human enzymopathy and assess its usefulness as an experimental model for a number of human diseases including hemolysis, metabolic muscle disease, hyperuricemia and gout and as a recipient of bone marrow transplantation and enzyme and gene replacement therapies.